Btrfs can mostly fo everything you would normaly use LVN or raid for natively.
Btrfs raid0 lets you combine any number of differently sized drives into one (just without the speed boost of traditional raid0 because with flexible drive sizes data is not symmetrical striped). And btrfs raid1 keeps every data duplicated, again with flexible number and sizes of drive (also with metadata on every drive).
The sytemd hooks (instead of the traditional busybox ones) then manage the one other task you use LVM for: unlocking multiple partitons (for example multiple raid partitons and swap) with just one password. Because the systemd encrypt function tries unlooking all luks partitions it finds with the first password provided and only asks for passwords for each partition if that doesn’t work.
PS: btrfs subvolumes are already flexible in size and don’t need predefined sizes. So the only things that need to be created separately are non-btrfs stuff like the efi system partition or a physical swap (which you can also skip by using a swap file instead of a partition).